1. Field of the Invention
The present invention relates to a device which is provided in an electronic still video camera, for example, and which reads an image developed on a recording medium by a scanning operation.
2. Description of the Related Art
Conventionally, silver halide photographic material is generally used as a material for recording an optical image. Silver halide photographic material has high optical sensitivity and high resolution, and the economical efficiency thereof is excellent. However, silver halide photographic material has drawbacks in that not only is the developing process cumbersome but also a visible image cannot be obtained at the same time as photography. A dry-type developing method has been developed to simplify the developing process. However, simultaneous development in which a visible image is obtained upon photography is impossible in the dry-type developing method.
On the other hand, as non-silver-halide photographic materials, there are known electrophotographic materials, diazotype photographic materials and free-radical photographic materials and so on. In these materials, however, there is no material which has advantageous characteristics like silver halide photographic material, while being able to simultaneously develop and keep a visible image. Note that, electrophotographic materials have been used mainly in copying machines, since they can perform dry-type development and can simultaneously develop an electrostatic latent image, which is obtained by exposure, using toner.
In such electrophotographic materials, recently, a photographic material has been developed in which a recording material made of the photographic material is electronically and directly developed similarly to a silver halide photographic material, so that the developed visible image can be immediately seen or recorded. Such a recording material in which a visible image is electronically developed is referred to as an electro-developing recording material in this specification.
Japanese Unexamined Patent Publication No. 5-2280 and U.S. Pat. No. 5,424,156, for example, discloses a recording material which is a combination of an electrostatic information recording material and an electric charge keeping medium, the electrostatic information recording material having a photoconducting layer and an inorganic oxide material layer, and the electric charge keeping medium having a liquid crystal display. In this structure, when the electrostatic information recording material is exposed while an electric voltage is applied to the electrostatic information recording material and the electric charge keeping medium, electric charge in accordance with the amount of incident light is generated in the electrostatic information recording material. Since the intensity of electric field applied to the liquid crystal display facing the electrostatic information recording material varies in accordance with the generated electric charge, an image corresponding to the amount of light distribution is indicated or developed on the liquid crystal display.
In a camera in which an electro-developing recording medium is mounted, it can not be checked whether or not the recording medium has been recorded until a reading operation in which one frame's worth of image signals is read out from the recording medium has been completed.
On the other hand, in the camera, when an image developed on the electro-developing recording medium is read out therefrom, an image signal corresponding to the image is temporarily stored in a memory, and is outputted to an external device. If the image developed on the electro-developing recording medium is read out therefrom while other image signals stored in the memory are read out therefrom, the image developed on the electro-developing recording medium cannot be stored in the memory, and thus the reading operation for the electro-developing recording medium is useless. Conversely, if an image stored in the memory is read out therefrom while another image developed on the electro-developing recording medium is read out therefrom to store the corresponding image signal in the memory, the image signals corresponding to the other image cannot be outputted to the external device. Namely, a meaningless image signal is outputted, and thus the desired image is not outputted to the external device.